1. Field of the Invention
The present invention relates to an electromagnetic relay.
2. Description of the Related Art
As the electromagnetic relay for shutting off direct currents, there has been a hermetically sealed relay, for example, disclosed in Japanese Patent Article 1.
Specifically, a plunger 9 contacts with or separates from a core center 4 according to magnetization or demagnetization of a coil 26 within a hollow cavity 40, and an armature assembly 8 and an armature shaft 10 integrated with the plunger 9 slide in a direction of the shaft, so that a movable contact disk 21 contacts with or separates from fixed contacts 22 and 22.
[Patent Article 1] International Patent Publication No. 510040/1997
In the above-mentioned hermetically sealed relay, however, after a voltage is applied to the coil 26 so to excite it, when the voltage stops in order to return the plunger 9, the eddy currents generated according to a change of the magnetic flux flow into the core center 4 to produce a new magnetic flux, which inhibits the return operation of the plunger 9. According to this, since the armature shaft 10 and the movable contact disk 21 cannot move away from the fixed contacts 22 and 22 quickly and the arc keeps for a while, there is a fear of damaging the contacts and there is a problem that a desired switching characteristic cannot be obtained.
Taking the above problem into consideration, the invention is to provide an electromagnetic relay that can perform a quick return operation of a movable iron piece free from a fear of welding the contacts by preventing the generation of magnetic flux due to the eddy currents.